Elevational differentiation of community-weighted seed regeneration strategies along a climate‒soil covariation gradient in alpine meadows

Compared with adult vegetative traits, seed traits characterize early life regeneration strategies but remain less integrated into community-level trait studies. Along alpine elevational gradients, climate and soil conditions often change simultaneously, complicating the interpretation of the environmental context of community regeneration. We examined six community-weighted seed traits in 60 quadrats nested within 12 alpine meadow plots across four elevations and three slope aspects on the eastern Qinghai–Tibetan Plateau. Community-weighted seed traits formed two distinct regeneration dimensions: a seed mass–germination capacity axis and a germination cue responsiveness axis. Elevational differentiation was concentrated primarily in germination capacity. Seed PC1, community-weighted germination percentage, and germination rate were higher at 3000 m than at the three higher elevations, whereas germination cue responsiveness showed no clear elevational pattern, suggesting that responses to specific germination cues were less consistently structured by the broad elevation-associated environmental gradient than overall germination capacity. Growing season temperature strongly covaried with the plot-level soil moisture–organic resource gradient. When evaluated separately, Seed PC1 was positively associated with both growing season temperature and the between-plot soil moisture–organic resource gradient, whereas Seed PC2 showed no detectable association with either climatic or soil gradients. Because temperature and soil conditions were strongly correlated, their associations with germination capacity could not be separated into independent climatic and edaphic effects. Alpine meadow communities differed primarily in terms of their germination capacity rather than their cue responsiveness along the elevational gradient. These contrasting seed-strategy dimensions were embedded within a coupled climate–soil gradient, highlighting the need to consider regeneration traits and environmental covariation together when interpreting alpine community assembly.